Report VideoDecoder status through ReadCB instead of through FilterHost.

media/base/filters.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Filters are connected in a strongly typed manner, with downstream filters
 // always reading data from upstream filters.  Upstream filters have no clue
 // who is actually reading from them, and return the results via callbacks.
 //
 //                         DemuxerStream(Video) <- VideoDecoder <- VideoRenderer
 // DataSource <- Demuxer <
@@ skipping 91 matching lines @@
   FilterHost* host() const { return host_; }
 
  private:
   FilterHost* host_;
 
   DISALLOW_COPY_AND_ASSIGN(Filter);
 };
 
 class MEDIA_EXPORT VideoDecoder : public Filter {
  public:
+  // Status codes for read operations on VideoDecoder.
+  enum DecoderStatus {
+    kOk,  // Everything went as planned.
+    kDecodeError,  // Decoding error happened.
+    kDecryptError  // Decrypting error happened.
+  };
+
   // Initialize a VideoDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // statistics_cb is used to update global pipeline statistics.
   virtual void Initialize(DemuxerStream* stream,
                           const PipelineStatusCB& status_cb,
                           const StatisticsCB& statistics_cb) = 0;
 
-  // Request a frame to be decoded and returned via the provided callback.
-  // Only one read may be in flight at any given time.
+  // Requests a frame to be decoded. The status of the decoder and decoded frame
+  // are returned via the provided callback. Only one read may be in flight at
+  // any given time.
   //
   // Implementations guarantee that the callback will not be called from within
   // this method.
   //
-  // Non-NULL frames contain decoded video data or may indicate the  end of
-  // the stream. NULL video frames indicate an aborted read. This can happen if
-  // the DemuxerStream gets flushed and doesn't have any more data to return.
-  typedef base::Callback<void(scoped_refptr<VideoFrame>)> ReadCB;
+  // If the returned status is not kOk, some error has occurred in the video
+  // decoder. In this case, the returned frame should always be NULL.
+  //
+  // Otherwise, the video decoder is in good shape. In this case, Non-NULL
+  // frames contain decoded video data or may indicate the end of the stream.
+  // NULL video frames indicate an aborted read. This can happen if the
+  // DemuxerStream gets flushed and doesn't have any more data to return.
+  typedef base::Callback<void(DecoderStatus, scoped_refptr<VideoFrame>)> ReadCB;
   virtual void Read(const ReadCB& read_cb) = 0;
 
   // Returns the natural width and height of decoded video in pixels.
   //
   // Clients should NOT rely on these values to remain constant. Instead, use
   // the width/height from decoded video frames themselves.
   //
   // TODO(scherkus): why not rely on prerolling and decoding a single frame to
   // get dimensions?
   virtual const gfx::Size& natural_size() = 0;
@@ skipping 12 matching lines @@
   virtual void PrepareForShutdownHack();
 
  protected:
   VideoDecoder();
   virtual ~VideoDecoder();
 
  private:
   // These functions will be removed later. Declare here to make sure they are
   // not called from VideoDecoder interface anymore.
   // TODO(xhwang): Remove them when VideoDecoder is not a Filter any more.
-  // See bug: crbug.com/108340
+  // See bug: http://crbug.com/108340
   virtual void Play(const base::Closure& callback) OVERRIDE;
   virtual void Pause(const base::Closure& callback) OVERRIDE;
   virtual void Seek(base::TimeDelta time,
                     const PipelineStatusCB& callback) OVERRIDE;
+  virtual FilterHost* host() OVERRIDE;
 };
 
 class MEDIA_EXPORT VideoRenderer : public Filter {
  public:
   // Used to update the pipeline's clock time. The parameter is the time that
   // the clock should not exceed.
   typedef base::Callback<void(base::TimeDelta)> TimeCB;
 
   // Initialize a VideoRenderer with the given VideoDecoder, executing the
   // callback upon completion.
@@ skipping 34 matching lines @@
 
   // Resumes playback after underflow occurs.
   // |buffer_more_audio| is set to true if you want to increase the size of the
   // decoded audio buffer.
   virtual void ResumeAfterUnderflow(bool buffer_more_audio) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_FILTERS_H_